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<head>
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    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
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     <link rel="stylesheet" href="./outer.css">
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    <style>
        div{
            background-color: aqua;
        }
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     <div style="width:100px;height:100px">块级元素</div>
</body>
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